Hello,
I am currently experimenting with creating multi-page PDFs with Acrobat 9 Pro from digital images (both TIFFs and JPEGs). I'm using a Mac, if that makes a difference. I have been asked by my boss to create versions in color and versions in grayscale.
I've been playing around with using Tiffs to make multi-page PDFs. I created several multi-page PDFs from the color (8-bit) tiffs, and then converted the tiffs to grayscale, and made another identical PDF in grayscale. The grayscale tiffs are a third of the size of the color tiffs, but for some reason, the grayscale PDF is twice as large as the color PDF. The issue is the same when creating the PDFs from JPEGs as well, only on a smaller scale. Can any shed light onto why that is, and if/how I can adjust this?
Thanks in advance
1) By default, in most profiles Distiller will use a higher ppi resolution for grayscale images than for color, so there's more to store even though each pixel requires less data.
2) If you're using a preset such as PDF/X, it will convert everything into CMYK - which of course puts back the other plates missing from a true K-space file.
3) If the TIFFs are in RGB and just desaturated to "visual" gray by your photo editor, they may be using all plates to retain the gamut (i.e. rich blacks instead of just the K-plate).
You can use Acrobat's Preflight and Output Preview tools to see what plates are being used in the PDF and what the resolution of a bitmap is after conversion to PDF.